linux-kernel - Re: [PATCH] lib: memmove: Use optimised memcpy if possible

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Message-ID: <CANc+2y7D0pTVZaJzot6ztC7iX2QGoUdkKrcptUTFOtAj_N2p8Q@mail.gmail.com>
Date:   Sat, 25 Nov 2017 22:52:04 +0530
From:   PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>
To:     open list <linux-kernel@...r.kernel.org>, dan.carpenter@...cle.com,
        mchehab@...nel.org, Paul Burton <paul.burton@...tec.com>
Cc:     PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>
Subject: Re: [PATCH] lib: memmove: Use optimised memcpy if possible

Hi,

On 4 October 2017 at 22:26, PrasannaKumar Muralidharan
<prasannatsmkumar@...il.com> wrote:
> When there is no overlap between src and dst use optimised memcpy if it
> is available.
>
> Signed-off-by: Paul Burton <paul.burton@...tec.com>
> Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>
> ---
> This change is a small part of a patch [1] from Paul Burton. I have
> added his Signed-off by. I do not know whether it is correct. Please let
> me know if it has to be changed, I will send a v2.
>
> This patch is boot tested with qemu for MIPS architecture by removing
> mips's memmove routine. This patch does not contain MIPS changes. I
> will try to find out why [1] was not taken already and figure out what
> to do.
>
> 1. https://patchwork.linux-mips.org/patch/14517/
>
>  lib/string.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/lib/string.c b/lib/string.c
> index 9921dc2..462ab7b 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -825,6 +825,17 @@ void *memmove(void *dest, const void *src, size_t count)
>         char *tmp;
>         const char *s;
>
> +#ifdef __HAVE_ARCH_MEMCPY
> +       /* Use optimised memcpy when there is no overlap */
> +       const char *s_end = src + count;
> +       const char *d = dest;
> +       char *d_end = dest + count;
> +
> +       s = src;
> +       if ((d_end <= s) || (s_end <= d))
> +               return memcpy(dest, src, count);
> +#endif /* __HAVE_ARCH_MEMCPY */
> +
>         if (dest <= src) {
>                 tmp = dest;
>                 s = src;
> --
> 2.10.0
>

Is there anything more that I have to do for this patch?

Regards,
PrasannaKumar